1. Field of the Invention
The present invention relates to optical fiber making processes and particularly to a novel method for reducing losses of germania dopant evaporated during chemical vapor deposition.
2. Description of the Prior Art
The use of germania as a dopant for increasing the index of refraction of a silica core of an optical fiber has been disclosed in U.S. Pat. No. 3,737,293, issued Jun. 5, 1973 and RE. 28,028, issued Jun. 4, 1974. In another known process described in copending U.S. Application Ser. No. 497,990, filed Aug. 16, 1974, a high index of refraction core layer of germania doped silica is formed by chemical vapor deposition within a lower index cladding tube to make an optical fiber preform. In this process it has been found that a large percentage of germania, up to about 70 percent, is lost by evaporation and carried away by a carrier gas.